Rounding Errors

[JamieLeaf]

Hey guys,
My teacher has been really unclear about rounding errors so I would just like to clear things up here. Lets say that you are doing a question and you find out the answer for part a and you've rounded the value to the required significant figures. For part b, which requires you to use your answer for a, do you use the value you obtained from part A (rounded to required sig figs) or do you need to use the exact unrounded value on your calculator to avoid rounding errors? Thanks!!

[chickan]

Pretty sure you use the exact unrounded answer in your working for part b, and then round it when you get your final answer for part B. If there's a part C, I would continue using the exact unrounded answer

[Sine]

Hey guys,
My teacher has been really unclear about rounding errors so I would just like to clear things up here. Lets say that you are doing a question and you find out the answer for part a and you've rounded the value to the required significant figures. For part b, which requires you to use your answer for a, do you use the value you obtained from part A (rounded to required sig figs) or do you need to use the exact unrounded value on your calculator to avoid rounding errors? Thanks!!

Always use exact values (although you can write them down to X decimal places)

So, if you get an answer for a as 3.21 but the actual value is 3.2087... you would insert the actual value in when calculating subsequent answers (but it is ok to write down the rounded form in your working out).

[DBA-144]

Always use exact values (although you can write them down to X decimal places)

So, if you get an answer for a as 3.21 but the actual value is 3.2087... you would insert the actual value in when calculating subsequent answers (but it is ok to write down the rounded form in your working out).

What if using those values gives you a different answer though? This could happen right?

[Bri MT]

What if using those values gives you a different answer though? This could happen right?

It could happen but they don't expect you to waste time writing out 10 or so digits

[dashnog]

In general, I stay by the rule to keep as many of my calculations as exact as possible and then round at the end using the appropriate amount of significant figures. It just saves the hassle.